1. Field of the Invention
The present invention relates generally to a stimulating medical devices and, more particularly, to an electrode assembly for a stimulating medical device.
2. Related Art
Hearing loss, which may be due to many different causes, is generally of two types, conductive and sensorineural. In some cases, a person may have hearing loss of both types. Conductive hearing loss occurs when the normal mechanical pathways for sound to reach the hair cells in the cochlea are impeded, for example, by damage to the ossicles. Conductive hearing loss is often addressed with conventional hearing aids which amplify sound so that acoustic information can reach the cochlea.
In many people who are profoundly deaf, however, the reason for their deafness is sensorineural hearing loss. This type of hearing loss is due to the absence or destruction of the hair cells in the cochlea which transduce acoustic signals into nerve impulses. Those suffering from sensorineural hearing loss are thus unable to derive suitable benefit from conventional hearing aids due to the damage to or absence of the mechanism for naturally generating nerve impulses from sound.
It is for this purpose that another type of auditory prosthesis, a COCHLEAR™ implant (also commonly referred to as COCHLEAR™ prosthesis, COCHLEAR™ devices, COCHLEAR™ implant devices, and the like, generally and collectively referred to herein as “cochlear implants”) has been developed. Stimulating auditory prostheses such a cochlear implants bypass the hair cells in the cochlea, directly delivering electrical stimulation to the auditory nerve fibers via an implanted electrode assembly. This enables the brain to perceive a hearing sensation resembling the natural hearing sensation normally delivered to the auditory nerve.
Despite the enormous benefits offered by cochlear implants, one potential disadvantage is that the implanted electrode carrier member is located within the internal canals of the cochlea, generally the scala tympani. Breaching the scala tympani may adversely affect the hydrodynamic behavior of the cochlea and/or damage existing hair cells thereby preventing or at least reducing the likelihood that any residual hearing will be preserved. This may be problematic for those persons who would benefit from use of a cochlear implant to improve hearing of relatively high frequency sound but who have some residual hearing of relatively low frequency sound. In such a case, the recipient is forced to decide whether it will be beneficial to sacrifice any existing residual capacity to hear relatively low frequency sounds to attain the benefits of a cochlear implant to provide hearing sensation of relatively high frequency sounds.